CZ88796A3 - Fuels for gas producers - Google Patents

Abstract

A gas developing agent, in particular for airbags, contains (A) at least one carbonate, hydrogen carbonate or nitrate of guanidine, aminoguanidine, diaminoguanidine or triaminoguanidine; (B) at least one alkaline or alkaline earth nitrate or ammonium nitrate as oxidising agent; and (C) at least one carrier selected among silicon dioxide, alkaline, alkaline earth or aluminosilicates, and/or at least one oxygen-supplying carrier selected among ferric oxide, cobalt oxides, manganese dioxide and cupric oxide, to moderate combustion and improve ash formation. This gas developing agent has improved combustion and ash formation.

Description

Fuels for gas generators

Technical field

The invention relates to solid fuels for gas generators based on guanidine compounds on suitable carriers.

BACKGROUND OF THE INVENTION

JP H5-254977 discloses fuels for gas generators based on triaminoguanidine, which may further comprise oxidizing agents such as nitrates, nitrites, chlorates and perchlorates of alkali and caustic earth metals; as an additional component there may be molybdenum sulfide. The advantage of using triaminoguanidine nitrate compared to sodium azide is its non-toxicity as well as the good stability of said substance, which in addition does not form any salt, which is characterized by sensitivity to friction and impact in contact with heavy metals. The rate of combustion of the fuel for the gas generator can be modified with respect to the compression pressure by adjusting the mixture to granules or tablets.

The disadvantages of existing fuels for gas generators are still insufficient controllability of combustion, further the development of toxic gases such as carbon monoxide and imperfect slag formation during combustion and, as a result, increased formation of dust, some of which enters the lungs.

In comparison with JP H5-254977, it is an object of the present invention to provide an improved fuel for a gas generator that allows combustion to be systematically controlled and treated to produce trapped slag during combustion while minimizing the formation of toxic gases.

The fuels for gas generators are to be stable in heat, easy to ignite, to burn quickly even at low temperatures, to be satisfactorily storable and to ensure a high gas yield. Further, there is an intention to reduce the size of the gas generator, thereby reducing the entire generator housing and, consequently, reducing its weight compared to known generators which operate using sodium azide.

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SUMMARY OF THE INVENTION

According to the present invention, these objectives are achieved by the fuel for the gas generator it contains

(A) at least one carbonate, bicarbonate or nitrate of guanidine, aminoguanidine, diaminoguadidine or triaminoguanidine,

(B) at least one alkali metal, caustic earth metal or ammonium nitrate oxidizing agent, and

(C) at least one carrier selected from the group consisting of silicon dioxide, alkali metal or caustic earth metal silicates, aluminum silicate and / or one oxygen delivery carrier such as iron oxide, cobalt oxides, manganese dioxide or cupric to control combustion and improve slag formation.

Guanidine, aminoguanidine, diaminoguanidine or triaminoguanidine carbonates, bicarbonates or nitrates may be used as component (A). Triaminoguanidine nitrate can be used advantageously, it is in fact nontoxic (LD ₅₀ is above 3500mg / kg, rats), is not hygroscopic, is slightly soluble in water, heat stable, burns at low temperature and is very insensitive to impact and friction. The gas yield of the combustion of triaminoguanidine nitrate is very high and this process generates a large amount of nitrogen.

If desired, 1 - 50% by weight of triaminoguanidine nitrate can be replaced by nitroguanidine, thus reducing the costs associated with component (A) and achieving a favorable combustion process since nitroguanidine compared to nitrate. W »HMW '* w triaminoguanidine burns slowly i.

As component (B) alkali metal nitrates of caustic earth metals, ammonium nitrate or mixtures thereof may be used. Preferably potassium nitrate is used. It is non-hygroscopic, non-toxic and its use is associated with a high combustion gas yield at low combustion temperature.

In the mixture of components (A) and (B), component (A) is present in an amount of about 20 to 55, preferably about 50 to 55% by weight; component (B) in an amount of from about 80 to 45, preferably 50 to 45% by weight. The proportion of component (A) is preferably 50-55% by weight and component (B) 50 to 45% by weight.

As component (C), silicon dioxide, alkali metal or caustic earth metal silicates, aluminum silicate or mixtures thereof can be used. Examples include Aerosil 200 and Aerosil 300, highly dispersed silicic acid and diatomaceous earth.

Iron (III) oxide, cobalt oxides, manganese dioxide and copper oxide, and mixtures thereof, can also be used as component (C). The preferred carrier to provide oxygen is iron (III) oxide.

In relation to the total amount of components (A) and (B), the proportion of component (C) is about 5-45, preferably about 8 - 20% by weight. When an iron-oxide carrier in function (C) is used as the oxygen delivery carrier, the amount thereof is about 20 to 40, preferably about 25-35% by weight, calculated on the total amount of components (A) and (B).

Component (C) has the task of adjusting the burning, i.e. adjusting its speed. At the same time, the formation of slag or melt is improved. Slag formation is absolutely necessary, for example when creating an air bag.

The air bag essentially comprises a gas generator housing with a gas generator fuel, usually in the form of tablets, and an initial initiator (electric igniter) for igniting the fuel in the gas generator, and then an air bag. Suitable detonators are described, for example, in U.S. Pat. No. 4,931,111. The air bag initially folded into a small package is filled after initial detonation with gases that are generated by combustion of the fuel in the gas generator and the final volume is reached within about 10 hours. up to 50 milliseconds. Leakage of hot sparks, molten material or solids from the gas generator into the gas bag should be largely avoided as this could result in destruction of the gas bag or injury to the occupants of the vehicle. This is achieved by the formation of slag.

At the same time, the formation of slag reduces the formation of dust constituents which may enter the lungs and which could escape from the air bag gas generator. The dust particles that get into the lungs have a diameter of about 6 µm or less. The oxygen-providing carrier further suppresses the formation of toxic gases such as carbon monoxide that could be formed during combustion.

Optionally, the gas generator fuel may further comprise component (D), a water-soluble binder at room temperature. Preferred binders are cellulose substances or polymers of one or more polymerizable olefinic derivatives, i.e. monomers. Examples of the cellulose group include ethers such as carboxymethylcellulose, methylcellulose ethers, especially methylhydroxyethylcellulose. In this case, CULMINAL ^(R) MHEC 30000 PR from Aqualon may be mentioned as a useful substance. Suitable polymers with binding properties are polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol and polycarbonate.

In proportion to the total content and amount of the substances (A) and (B), component (D) is used in an amount of about 0.1 to 5, preferably about 1.5 to 2.5% by weight.

The binder (D) has the function of a desensitizer and processing aid, in particular in the preparation of a granular material or tablet for a gas generator. It is also intended to reduce the hydrophilic nature of the gas generator fuel and to stabilize the fuel.

Tablets or granulated fuel generator material may be prepared by known methods, for example by hot pressing, extrusion, rotary compression in a press or tabletting machine. The size of the granules or tablets depends on the required burning time in one or another application.

DETAILED DESCRIPTION OF THE INVENTION

The calculated amounts of triaminoguanidine nitrate, possibly also nitroguanidine, as well as potassium nitrate and optionally cellulose ether, are dissolved at 90 ° C in as little water as possible and mixed with ferric and / or medium-sized silica in the solution. 1 µm. After pre-drying with mechanical stirring at 60 ° C and 16 hPa, the mixture is still wet-ground to a small particle size and after drying at 60 ° C it is compressed in a tabletting machine into tablets with a diameter of 6 mm and a thickness of 2 mm.

The mixtures tested are shown in Table I. Mixture 1 contains no silica at all and mix 5 does not contain any iron oxide. For comparison, mixture 6 contains neither iron oxide nor silica.

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-6Table I

Composition of mixtures in percent by weight

1 2 3 4 5 6 Trinitro Nitrate 39.1 39.1 39.1 29.1 47.3 53.0 guanidine Nitroguanidin - - - 10.0 - - Potassium nitrate 30.9 30.9 30.9 30.9 40.7 47.0 Iron oxide 30.0 20.0 14.0 14.0 - Silica - 10.0 14.0 14.0 12.0 - ' Cellulose ether - - 2,0 2,0 - -

Table II provides an overview of the reaction parameters determined by the calculations. The high reaction temperature is recorded in mixture 5, and in particular in mixture 6,

-7Table II: Calculated® Values

Oxygen fluctuation% 2.13 + 1.13 -1.84 -1.57 + 0.25 +0.84 Volume ml 1000 1000 1000 1000 1000 1000 Filling density (g / ml) 0.1 0.1 0.1 0.1 0.1 0.1 Pressure, bar 427 444 470 457 654 810 Temperature K · -> - < íT c Ό C C Mol used of gases mol / kg 21.1 22.6 23.9 23.4 27.5 28.8 flash point J / g 3365 3092 2353 2513 3352 4566 Taboo 1 to a III: -

Reaction products at 298 K, freezing temperature 1500 K

Merging- 1 2 3 4 5 6 to (%, w / w) co ₂ 3.604 10.086 11.538 13.228 12.408 3.768 h ₂ o 18.952 18.817 18.828 17.711 22.935 26.692 n ₂ 27.219 27.219 27.217 26.735 33.383 37.596 WHAT 0.000 0.134 1.283 1.223 0.000 0.000 h ₂ 0.000 0.017 0.139 0.109 0.000 0.000 NO 0.001 0.000 0.000 0.000 0.009 0.018 ° 2 0.001 0.000 0.000 0.000 0.248 0.826 HCN 0.000 0.000 0.000 0.000 0.000 0.000 nh ₃ 0.000 0.000 0.003 0.002 0.000 0.000 KOH 0.086 0.000 0.003 0.003 0.053 0.101 K ₂ CO ₃ 21.014 0.000 0.000 0.000 0.150 31.997 FeO - - 12.597 12.537 - - Fe ₂ O ₃ 3.726 0.000 0.000 0.000 - 0.000 Fe ₃ O ₄ 25.396 19.331 0.000 0.000 - 0.000 K 2 S 3 O 3 - 23.572 23.572 23.572 30.813 - SiO ₂ - 0.820 4.820 4.820 - -

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Table 8 shows the results of the tests taking into account degradation tendencies, stability, slag formation and ignition of various mixtures. The compositions 1 to 5 are distinguished by very good ignition behavior, especially with regard to the extremely stable, high combustion rate. Comparative mixture 6 was observed to be insufficient to form slag and also to be insufficient to burn; this mixture contained neither silica nor iron oxide as component (C).

Table IV:

Test results

Mixture 1 2 3 4 5 6 Decomposition temperature ° C *) 207 178 203 - Measurement conditions: Heating rate 2 ° C / min 15 ° C below decomposition temperature from Persistence: Test Holland Sample weight: 2.5 g Test temperature: 105 ° C Test time: 72 hr Weight Loss (% Mass) 0.28 0.40 0.13 - Slag formation + + + + + + + + + + Burning behavior + + + + + + + + Notes: ++ very good, + good, - do not comply

*) mixture 1 was tested by another method

Mixture stability test 1

1. Differential thermal analysis:

Equipment: HERAEUS - FUS-O-MAT

Heating rate 10 ° C / min, initial sample weight 10 mg Result: conversion of potassium nitrate. 129/130 ° C Onset of exothermic reaction: 168 ° C

2. Differential thermogravimetry

Equipment: LINSEIS - Simultan DTA / TG

Heating rate: 5 ° C / min, sample weight initially 20 mg

· Conversion of potassium nitrate: 127 ° C start of exothermic reaction: 155 C explosive combustion: 158 ° C,

Combustion test 1:

The combustion test of mixture 1 was carried out in a normal aluminum gas generator housing for air cushion 60 l, provided with a pressure measuring hole, all in a 60 l can. Test temperature in test 1 was -35 ° C, propellant fill weight 51.0 g. The mixture was 6 mm in diameter and 2 mm in thickness.

In Fig. 1, the pressure in the combustion chamber, expressed in 10 ⁵ Pa as a function of time after detonation, in milliseconds for Test 1.

The pressure builds up in about 1.5 milliseconds and drops to half the highest pressure in about 27 milliseconds. The maximum pressure of 1.88 χ 10 ⁷ Pa is reached in 12.3 milliseconds.

Analysis of the toxic components of the gas as produced, in ppm:

Carbon monoxide 300, ammonia above 70, nitrogen oxides 60

Combustion test 2:

This combustion test of mixture 2 was carried out in an aluminum gas generator Euro 35 for an air cushion of 35 liters, equipped with a pressure measuring opening placed in a 60 L metal canister. Test temperature 2-35 ° C, test 3 + 20 ° C. The propellant fill weight in test 2 was 41.0 g, in test 3 30.0 g. The propellant fill consisted of tablets> WP

- 10 with a diameter of 6 mm and a thickness of 2 mm.

Na vyobr. 2 is the pressure in the combustion chamber, expressed in units of 10 ^s Pa as a function of time after detonation, in milliseconds for test 2.

The pressure builds up in about 1.5 milliseconds and drops to half the maximum pressure in about 27 milliseconds. The highest pressure was 1.45 x 10 ⁷ Pa and was reached in 15.7 milliseconds. 3 is the pressure in the combustion chamber, expressed in units of 10 ^s Pa as a function of time after detonation, in milliseconds for test 3.

The pressure builds up in about 1.5 milliseconds and drops to half the maximum pressure in about 27 milliseconds. The maximum pressure of 1.33 χ 10 ⁷ Pa was reached in 7.5 milliseconds.

The propellant mixture of the gas generator according to the invention is composed of non-toxic, readily obtainable and inexpensive components, the processing of which is not associated with problems, their heat stability also means good storage stability. Despite the low combustion temperature, the ignition of the mixture is good. This burns rapidly and is associated with a high yield of gases produced with very low levels of undesirable components such as carbon monoxide and nitrogen oxides. The compositions of the invention are particularly suitable for use as gas generating agents in various air bag systems, as extinguishing agents or propellants. In addition, these components are easily recyclable.

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Claims (12)

PATENT CLAIMS 9 6 J 11 N Z m; oa Fuel for a gas generator of at least one carbonate, hydrogen carbonate or guanidine, aminoguanidine, diaminoguanidine or N-guanidine in an amount of from 20 to 55% by weight, (B) ) at least one alkali or caustic or ammonium nitrate nitrate as an oxidizing agent in an amount of 80 to 45% by weight, and to reduce combustion and improve slag formation in an amount of 5 to 45% by weight, calculated on the total amount of components (A) and (B) (C1) at least one carrier from the group comprising silicon dioxide, alkali metal or caustic earth metals or aluminum silicates and / or (C2) one carrier providing oxygen to the system from the group comprising iron oxide, cobalt oxides, manganese dioxide and% * oxide Copper. The gas generator fuel according to claim 1, wherein component (A) is present in an amount of from 50 to 55% by weight, component (B) in an amount of from 50 to 45% by weight and component (Cl) and / or (C2). %, based on the total amount of components (A) and (B) in an amount of 8 to 20% by weight. The gas generator fuel according to claim 1 or 2, wherein component (A) is triaminoguanidine nitrate. The gas generator fuel according to any one of claims 1 to 3, wherein component (B) is potassium nitrate. The gas generator fuel of any one of claims 1 to 4, wherein component (C1) is silica at a pH of about 7. 6. The gas generator fuel according to claim 1, wherein component (A) is from 99 to 50% by weight of triaminoguanidine nitrate and from 1 to 50% by weight of nitroguanidine calculated on the total amount of component (A). • ’1 The gas generator fuel according to any one of claims 1 to 6, wherein the component (C2) is iron oxide. 8. The gas generator fuel according to claim 7, wherein the iron oxide is used in an amount of 20 to 40% by weight, preferably 25 to 35% by weight, based on the total J amount of components (A) and (B). j The gas generator fuel according to any one of claims 1 to 8, further comprising, in addition, component (D), a water-soluble binder. The fuel of claim 9, wherein the binder is a cellulose ether such as carboxymethylcellulose, methylcellulose ether, and in particular methylhydroxyethylcellulose or a polymer of one or more polymerizable olefinic monomers. The gas generator fuel according to claim 9 or 10, wherein the binder is used in an amount of 0.1 to 5, preferably 1.5 to 2.5% by weight, based on the total weight of components (A) and (B). Use of the fuel according to any one of claims 1 to 11 as a means for generating gas for air cushions, as a fire extinguishing agent or as a propellant.